In the early 1700s, France and Spain began disputing their New World international boundary that included this area; each nation claimed what is now Texas. When the U.S. purchased the Louisiana Territory from France in 1803, the boundary was still in dispute. Leaders agreed to a neutral area between the Arroyo Hondo and the Sabine River, and the 1819 Adams-Onís Treaty formally defined the border. When Texas became a republic in 1836, it appointed a joint commission with the U.S. to survey and mark the established boundary from the Gulf of Mexico up the Sabine River and on to the Red River. John Forsyth represented the U.S., and Memucan Hunt represented Texas in the work, which proved to be long and difficult.
The survey crew began the demarcation process on May 20, 1840 at the Gulf, placing a 36-foot pole in the middle of a large earthen mound. Proceeding north, they placed eight-foot posts denoting the number of miles from the 32nd parallel. Upon reaching the parallel, they placed a granite marker on the west bank of the Sabine River. From that point, they traveled due north to the Red River, completing their work in late June 1841.
As a result of erosion, the first granite marker on the Sabine fell into the river long ago, but a second granite marker on the northward path of the surveyors had been placed here
to mark the north-south meridian. This is the only known marker remaining, and it is believed to be the only original international boundary marker within the contiguous U.S. Today, the border between Texas and Louisiana follows the Sabine River to the 32nd parallel, at which point it connects to the boundary established by Hunt and Forsyth. The Texas Historical Foundation purchased this site to provide public access to the early boundary marker.